STONEHENGE, England — Thousands of neo-Druids, New Age followers and the merely curious flocked to Stonehenge on Sunday, beating drums, chanting and dancing in celebration of the longest day of the year.

The ancient stone circle at the prehistoric monument in southern England is the site of an annual night-long party — or religious ceremony, depending on perspective — marking the northern hemisphere's summer solstice.

"There has been a great atmosphere and where else would you want to be on midsummer's day?" said Peter Carson of English Heritage, who is in charge of the monument.

Camera flashes bounced off the stones through the night until patchy rays of sunlight peaked through the clouds at 4:58 a.m. BST. A weak cheer went up as dawn broke and an estimated 35,000 people, some of them wrapped in blankets, greeted the sunrise.

About 30 people arrestedPolice arrested about 30 people on charges including drug offenses, assault and drunk and disorderly conduct, but said the event was largely peaceful.

"They come for a complete range of reasons," said archaeologist Dave Batchelor of English Heritage, the site's caretaker. "Some belong to the Druidic religion and think of it as a temple, others think of it as a place of their ancestors, or for tranquility and others come to see it as a way to celebrate the changing of the seasons."

Stonehenge, which sits on Salisbury Plain about 80 miles (130 kilometers) southwest of London, is one of Britain's most popular tourist attractions, visited by more than 750,000 people a year. It was built in three phases between 3,000 B.C. and 1,600 B.C.

Mystery surrounding the monument has long prompted speculation about its original function and gives it even more of an allure, Batchelor said.

Some theories hold that the stone circle was a grave site because 350 burial mounds surround the structure.

In May, archaeologists found evidence indicating that pilgrims perceived the stones to have healing powers. And some assert that the structure was part of an ancient astronomical calendar.

Still other experts believe the stones were aligned by a sophisticated sun-worshipping culture that possessed the ingenuity to move the several-ton stones, some of which came from 150 miles (240 kilometers) away in the Preseli Mountains in Wales.

No records on monumentBut because it was built so long ago, there is no record of why the monument was erected, said Batchelor.

"All of that sort of stuff we don't have, so when it comes to ascribing a modern-day reason depends on the viewpoint ... that's the fascination," Batchelor said.

Libby Davy, 40, an Australian living in Brighton, in southern England, was attending the solstice for the first time with friends and her 8-year-old daughter. She wore sparkling dust on her face and wrapped a monkey doll around her neck as she took part in the festive mood.

"It's kind of a pilgrimage," she said. "As a sculptor, I can't help being interested in the stones — they're historic, spiritual — people went to a huge effort to put them here not anywhere else. Why here? And why this configuration? It's fascinating."

The solstice is one of the few times during the year that visitors can get close enough to touch the rocks. With record numbers attending the free festival because it falls on a weekend, extra police officers were on patrol.

Frank Somers, 43, an antique salesman, said he and other Druids came to Stonehenge to honor their ancestors.

"It's the most magical place on the planet," he said. "Inside when you touch the stones you feel a warmth like you're touching a tree not a stone. There's a genuine love, you feel called to it."

Carnival atmospherePolice closed the site in 1984 after repeated clashes with revelers. English Heritage began allowing full access to the site again in 2000 and the celebrations have been largely peaceful.